WASHINGTON, Dec 6 (Reuters) - President Donald Trump's administration on Thursday relaxed rules championed by former first lady Michelle Obama aimed at making U.S. school lunches healthier, a move that will affect institutions that feed 30 million children annually.

Agriculture Secretary Sonny Perdue, delivering on a promise he made when he took office in May 2017, said schools under the current rules faced challenges serving meals that were both appetizing and nutritious.

"If kids are not eating what is being served, they are not benefiting, and food is being wasted," Perdue said in a statement.

The Trump administration has vowed to slash regulations, which it says are burdensome for industries such as oil and coal, and has already rolled back a number of Obama-era rules as part of its business-friendly agenda.

The 2010 Healthy, Hunger-Free Kids Act was championed by Michelle Obama and became a rallying cry for her critics after it set school lunch maximums for calories, cut sodium and artery-clogging trans fat, and required more fruits, vegetables and whole grains.

The new rules will provide the option to offer flavored, low-fat milk to children and more time to reduce sodium levels in school meals.

Healthy-lunch proponents expressed the most concern about relaxing efforts to reduce excessive dietary sodium, which is linked to high blood pressure, heart attacks and strokes.

The federally funded U.S. school lunch program, started by President Harry Truman in the 1940s, is overseen by the U.S. Department of Agriculture and feeds more than 30 million, mostly low-income, children. (Reporting by Humeyra Pamuk; Editing by Peter Cooney)

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